Personally I don't see what is so wrong with Flickr. Tons of traffic should make up for, at least in part, poor compression. And if you pay for Flickr people can see the original sized image if they want to see it. If someone is looking at your site from an iPhone you don't want to saddle them with 10000x8000 pixel image. I just feel that Flickr gives the most robust offering coupled with significant web traffic.
With that being said, I don't host my portfolio on any open site, I have my own website. Flickr, Smugmug, et al. is great to show off work and snaps, but Im not sure if I think a portfolio should be on free or open site. My 2 most viewed images on Flickr are a funny shot of a sign and a shot of my tattoo. Not really things I want in my portfolio that a client might be looking through. Thats just IMO though, YMMV.